Hey there, Margaret! Welcome back to the Disney Parks Moms Panel.
As a lifelong Floridian, I can tell you spring is a perfect time of year here in my home state. The rainy season is still several weeks away, the days are warm, the nights are...well, also warm, but not as muggy as they'll be in the summer. It's a beautiful time to visit Walt Disney World.
The crowd levels in April are largely driven by where Easter occurs on the calendar that year. We'll have an early Easter in 2016, with the holiday falling on March 27. Because of that, many schools should be finished with Spring Break by early April. I suspect that the crowd calendars are factoring in the early Easter and coming up with crowd levels that will look a lot more like the beginning of May.
I hope this helps with your planning, Margaret. It can be hard to pinpoint the exact right time to visit Walt Disney World, but it sounds like your schedule will work well for you. Please do stop by again if you have any more questions!
Keep Disney Dreaming,
Kathy K.